Strut cathode support



Oct. 1, 1957 I w. R. WHEELER v STRUT CATHODE SUPPORT 2 Sheets-Sheet 1Filed April 19, 1954 INVENTOR WILLIAM R. WHEELER ATTORNEY Oct. 1, 1957w. WHEELER 2,808,529

- STRUT CATHODE SUPPORT Filed A ril 19, 1954 2 Sheets-Sheet 2 INVENTORWILLIAM R. WHEELER United States Patent 2,808,529 STRUT CATHODE SUPPORTWilliam R. Wheeler, Wantagh, N. Y., assignor to Sylvania ElectricProducts Inc., a corporation of Massachusetts Application April 19,1954, Serial No. 424,226 3 Claims. (Cl. 313--289) This invention relatesto electronic tube structure and particularly to the means for mountingthe cathode in proper position relative to a grid and anode.

In the manufacture of stack tubes, i. e., those employing planarelements which are sandwiched together, difficulty has been found infixing the elements in proper spaced relationship to one another. In thecase of a heated cathode, where one is employed, and where parts arevery closely spaced an additional problem arises due to the expansion ofthe cathode when heated. Provision must be made for such expansion andyet in a direction to not materially affect the spacing betweenelements, as between the cathode and grid. Another problem is toproperly support the cathode and yet prevent excessive heat conductionaway from the cathode through its support. Furthermore the structure ofthe tube should be simple to allow for ease in manufacture.

It is an object of this invention to provide, in a sandwich type tubemount, a simple support means for the cathode.

It is a further object of this invention to utilize the support means asa suitable spacer between the cathode and grid.

It is yet another object of the invention to still further utilize thecathode support means as a medium to clamp the parts of a tube mounttogether.

Further objects will become apparent after reading the followingspecification in the light of the accompanying drawings in which:

Fig. 1 is an end elevation of an electron tube mount in a position on atube base.

Fig. 2 is an enlarged view of a composite electrode utilized in themount, parts being sectioned away, and

Fig. 3 is an exploded view of the assembly of Fig. 1.

Referring to the drawings more in detail, at there is shown a tube base,or stem preferably of ceramic material such as alumina, having pin leads12 embedded therein, on which the mount is secured.

The mount here illustrated is a double triode comprised of a cathodesleeve 16 and two grid-anode structures 18. The cathode sleeve is of therectangular sleeve type with emissive surfaces 20 on opposite faces ofthe cathode. Within the sleeve is the heater 22 suitably tabbed, as at24, with the tabs welded to two of the stern leads.

Each of the grid-anode structures comprises a rectangu lar ceramic wafer26 preferably of zircon with a recess 28 extending inward from one face30 of the ceramic. The bottom only of the recess and the face 30 arecoated with an electro-conductive material such as a film ofmoly-manganese 31 (e. g. 80 parts molybdenum, 20 parts manganese) andintegrally associated with the outer coated face is a grid structure,here shown as made of tungsten wires 32. To reduce leakage between thegrid structure and the coating on the bottom of the recess, the ceramicis slitted longitudinally at 34, walls of the slits being prolongationof side walls of the recess and the end portions of the recess aredeepened and enlarged as at 35 to increase the resistance betweencoatings 31. The bottom coating is electrically secured to pins 36passing through the ceramic. The bottom coatings form anodes of the tubestructure. The grid is provided with a conducting tab 38 of molybdenumor the like brazed to the grid surface and appropriately welded to alead 12.

In order to mount parts in suitable spaced apart but fixed relationshipand yet permit proper expansion of parts of the mount, there is provideda pair of sheet metal straps 40, one near each end of the mount. Thestraps are pre cision stamped to shape and size and are of a thin metalhaving low thermal conductivity. Each stamping has two parallel runners42 and a bridge 44. The bridge has an olfset portion 46 in the plane ofthe bridge centrally of the length of the bridge. The distance betweenthe outside edge 48 of the offset portion and the opposed edge 50 of thebridge is equal to the spacings of the ceramic wafers from one anotherand the offset in the bridge is designed to space the cathode equallyfrom each grid. To secure the cathode sleeve on the bridges with minimumheat transfer, the bridges at the recessed portions are edge welded tothe sleeves as at 52. To clamp the assembly together the free ends ofthe runners are bent around the outside faces of the ceramic wafers 26,preferably while heating the runners as by placing the electrodes of awelding machine across opposite ends of a runner. The while the strap isstill hot, the runner ends can be bent around the wafers 26. The runnersare tight enough about the wafers to prevent separation of parts yetloose enough to allow slippage of a strap on heating and cooling of thecathode with consequent expansion and contraction thereof. With arectangular cathode very little expansion takes place in the directionof the grids. Therefore, the tube constants are suitably maintainedthrough the range of operating temperatures of the tube.

Selected leads are surmounted by plates 54 to which the pins 36 arewelded and a getter 56 is provided on the mount, thus completing theassembly.

Having thus described my invention what is claimed as new is:

1. A support element for a stacked tube comprising a sheet metal memberhaving two parallel equal rectangular runners and a bridge therebetweensubstantially midway of the length of the runners, the bridge having anoffset portion in the plane of the bridge substantially midway of thelength of the bridge.

2. A stacked tube mount comprising an electrode, a cathode sleeve and asupport member of thin sheet metal, said support member having a pair ofparallel runners and a bridge between the runners, the cathode sleevebeing secured to an edge of the bridge and the runners having bentportions embracing the electrode, the width of the bridge between theedge which the cathode sleeve is secured and the contact of the bridgewith the electrode determining the spacing of the cathode sleeve fromthe electrode.

3. A stacked tube mount comprising a pair of electrodes, a cathodesleeve, rectangular in cross section, and a support member of thin sheetmetal, said support member having a pair of parallel runners and abridge between the runners, the bridge having an offset portion midwayof its length, the cathode sleeve being secured to the bridge member atsaid offset portion to an edge of the bridge, the planes of the oppositeedges of the bridge being spaced apart a distance equal to the desiredspacing of the electrodes, with the faces of the cathode sleeve lyingwithin and equal distances from said planes, the runners having theirfree ends embracing the electrodes.

References Cited in the file of this patent UNITED STATES PATENTS1,597,643 Wiegner Aug. 24, 1926 1,783,623 Massie Dec. 2, 1930 2,148,538Depew et al. Feb. 28, 1939 2,414,805 Fay et al. Ian. 28, 1947 2,481,026Law et al Sept. 6, 1949 2,562,236 Hoagland et al. July 31, 1951

